This invention relates to methods for sealing leaks in pipe joints.
The most common type of joint in pipes carrying natural gas is known as a lead/yarn joint. This joint consists of a bell-shaped end region on one section of the pipe which receives into it an end region of the adjacent section of the pipe. The annular void between the end regions of the two sections is packed with a hemp material to form a gasket. Over this is provided a lead O-ring which extends between the gasket and the region external of the pipe. The lead O-ring is applied to provide mechanical strength to the seal in the joint.
The hemp used as a gasket contains about 75% to 80% water which gradually evaporates therefrom. This causes the gasket to shrink and decay. In addition, movement of the ground causes the lead O-ring to distort. This results in the escape of gas.
In view of the fact that much of this piping was laid at the turn of the Century, many of the gaskets in the pipe sections have decayed to allow gas to escape.
Several methods are used in order to seal leaking pipes. One method involves the application of a steel mould around the joint into which a curable resin is injected and allowed to set. Unfortunately, a disadvantage of such systems is that the steel moulds are expensive, and it is often difficult to remove them after the leak has been repaired.
Another method involves attaching an elongate member of C-shaped profile around the leaking joint, such that the member extends from one pipe section to the other. The member is provided with a socket to allow the escape of gas, and is secured to the pipe sections at the joint by means of resin or other suitable material. A plug is screwed into the socket to seal the leak. Unfortunately, the efficiency cannot be guaranteed, because ground movement can often cause the repair to fail.
A third method involves the injection of an acrylic material into the gasket. This requires complete saturation of the gasket in order for the seal to be effective. Unfortunately, the complete saturation of the gasket cannot be guaranteed and the repairs are often ineffective.
According to a first aspect of this invention there is provided a method for repairing a leak in a pipe joint between first and second pipes having a gasket at said joint, the method comprising forming a passage through the wall of the first pipe, forming a space in said gasket communicating with said passage, and thereafter injecting a sealant into said space via said passage, whereby the fluid can repair the leak
The passage may be formed by drilling. In one embodiment the aperture may be formed at an angle between tangential and perpendicular to the pipe wall. Preferably, the angle is between 20xc2x0 and 70xc2x0 to a line perpendicular to the pipe wall, more preferably between 30xc2x0 and 60xc2x0 to said line.
The step of forming the space in the gasket may include forming a second passage which may extend substantially circumferentially around the gasket. The first and second passages may be formed to extend to a region beyond said leak, preferably substantially wholly around the pipe.
In one embodiment, the step of forming said space in the gasket may further include inserting a space forming member into the pipe, preferably via said first passage, and applying a force thereto. The force may be a rotational force applied transverse to the intended direction of movement of the space forming member into the seal.
The space forming member may comprise an end piece, adapted to drill into said gasket, and elongate drive means extending from the end piece, whereby rotation of the drive means can cause rotation of the end piece, thereby causing the end piece to drill into said gasket. The end piece may be a drill bit which may be helical in configuration. The drive means may be a flexible member, for example a flexible cable.
In one embodiment, the flexible cable may be arranged within a tubular member. An urging means may act to urge the cable towards on of the walls of the pipe sections, preferably an outer wall. The urging means is preferably elongate and may extend from one end region to the other end region of the tubular member. Preferably, the urging means is fixed at said one end region of the tubular member adjacent the end piece.
The urging means may be in the form of a flexible tape, suitably formed of a material more rigid than the drive means or the tubular member, for example, steel. The urging means may be adapted to push on the cable in a direction transverse to the direction of motion thereof as the cable passes through the gasket.
Preferably, the second passage is so formed that rotation of the end piece causes said end piece to move around the periphery of the gasket. The end piece may be so shaped the rotation thereof causes it to move in a desired direction, suitably towards the adjacent end of the pipe section.
Where the pipe joint includes an end member adjacent the gasket, the step of forming said pathway may include forming said pathway adjacent the end member, preferably between said end member and the gasket. The end member may be an O-ring.
In another embodiment, the step of forming said pathway may include injecting a solution into the first pipe, the solution being suitable for dissolving at least some of said gasket. The solution may comprise an organic solution capable of dissolving at least some of the gasket. The organic solution may be selected from a solution of micro-organisms, a solution of exacted enzyme powders, and a solution comprising a mixture of micro-organisms and extracted enzyme powders. The micro-organisms are advantageously capable of dissolving at least some of the gasket by digesting at least some of the gasket. The micro-organisms may be selected from one or more of cellulase, hemicellulase, drielase and other suitable micro-organisms.
Means may also be provided for deactivating the abovementioned solution to halt the dissolving of the gasket. Said controlling means may comprise a deactivating solution to deactivate said solution. The deactivating solution may comprise one or more acids, one or more alkalis and/or one or more chemical inhibitors adapted to disable micro-organisms.
Means for directing sealant flow may also be provided. Said directing means may be adapted to direct said first mentioned solution before the sealant is injected, whereby the first mentioned solution is directed to form a path in a desired direction. Alternatively, the directing means may be adapted to direct the sealant.
Where the directing means is adapted to direct the first mentioned solution, the directing means may comprise magnetic means. In one embodiments the magnetic means may apply a magnetic field, whereby the micro-organisms can align themselves with said magnetic field to be directed in a desired direction preferably to form a path.
Where the directing means is to be applied to the sealant, the directing means may include a magnetic material in the sealant, said material being capable of being acted on by a magnetic field by said magnetic means.
The injection of said sealant may be by injection means, for example a static mixer and a syringe. The sealant may comprise a first component comprising a curable sealing material, and a second component comprising a curing agent. The components may be injected through the mixer to the pipe via said aperture.
At least one of the first or second components may be adapted such that the sealant cures after a pre-selected period has elapsed. This has the advantage in the preferred embodiment of eliminating or mitigating the reliance upon internal pipe conditions assisting the cure. This also provides the advantage in the preferred embodiment that the delay allows time for the injected sealant to flow to the leak.
Materials suitable for use as sealants are two part thermosetting methacrylate materials.
According to a second aspect of this invention, there is provided a method for sealing a pipe, comprising applying sealing means externally of the pipe across the joint. The sealing means may be in the form of a putty, for example a polyurethane putty. The sealing means may comprise a first component in the form of a curable material, and a second component comprising a curing agent.
The sealing means may be applied around the pipe.
After said sealing means has been applied to the pipe, compression means may be applied over the sealant to compress the sealing means. The compressing means may be in the form of a plastic film, which may be applied under tension to the pipe. The plastic film may be adapted to change colour when appropriate tension has been applied thereto. Desirably the film may change from clear to white when the appropriate tension has been applied.
An example of a suitable sealant is one sold under the trade mark POLYFORM by M W Polymers Limited. An example of a film which can be used is one sold by M W Polymer Products Limited under the trade mark POLYFORM wrapping film.
This second aspect of the invention may be provided as a secondary seal after the above first mentioned aspect has been carried out.